Seven people have been killed in violence after a protest against the result of the Iran election, according to reports.The clashes happened after hundreds of thousands of supporters of the defeated presidential candidate Mirhossein Mousavi held a rally in the capital Tehran.
State-run Radio Payam announced: "Several thugs wanted to attack a military post and vandalise public property in the vicinity of Azadi Square.
"Unfortunately seven people were killed and several others wounded in the incident."
More protests are planned for today, following President Mahmoud Ahmadinejad's victory in an election the Mousavi supporters claim was rigged.
Speaking for the first time about the violence, Barack Obama expressed his concern.
He said: "I am deeply troubled by the violence that I've been seeing on television.
"The democratic process, free speech, the ability of people to peacefully dissent - all those are universal values and need to be respected."
Mr Obama pledged to continue pursuing tough, direct dialogue with Iran despite differences with Mr Ahmadinejad.
He stressed that the US respected Iran's sovereignty and could not judge how the election was run because neither American nor international observers were present.
"The Iranian government says that they are going to look into irregularities that have taken place," he said.
"It's important that moving forward, whatever investigations take place are done in a way that is not resulting in bloodshed and is not resulting in people being stifled in expressing their views."
In a message to the protesters, Mr Obama said: "To those people who put so much hope and energy and optimism into the political process, I would say to them that the world is watching and inspired by their participation, regardless of what the ultimate outcome of the election was."
Despite the unrest in Iran, Mr Ahmadinejad travelled to Russia for a regional summit, although he had delayed his visit by a day because of the protests.
Mr Mousavi and another defeated candidate, Mohsen Rezai, are due to meet Iran's Guardian Council later after they filed official complaints against the election result.
The 12-member legislative body, which oversees elections, has 10 days to either endorse or reject the outcome of the vote.
